This is a proposal to improve the breath test for the detection of Helicobacter pylori in order to facilitate the diagnosis of gastrointestinal infections (ulcers, gastritis) associated with this microbe. As the NIH Consensus Panel did not recommend routine testing because of issues relating to cost, availability, and practicality, the objective of this proposal is to overcome these issues by using a gas chromatograph-mass spectrometer (GCMS) instead of an isotope ratio mass spectrometer (IRMS) to analyze for 13-CO2. By using a bench-top BCMS in the selected ion monitoring (SIM) mode, the goal is to perfect this method for routine hospital and commercial application. The specific aims are to 1) reduce the cost of SIM/GCMS analysis by automating sample injection, 2) improving sample collection by designing and testing a device for filling pre-capped vials that fit the automatic sampler, and 3) trying to reduce the cost and increase the accuracy of breath tests.